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Full text of "US Patent 2600263: Arsenic activated zinc sulfide phosphor and method for making same"

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Patented June 10, 1952 2,600,263 

UNITED 

STATES PATENT OFFI!CE 

2,600,263 
ARSF, NIC" ACTIVATED ZINC S3LFIDE P-H(S- 
PHOR AND METHOD FOR' MAKGï 
Jerome S. Prener» Schenectady, N. Y., assigner te 
General Electric Company,,, a corporai0n 0f 
New York • 
No, Drawing. Application January 24, 1951, 
SerialNo. 
8 Claires. (CI. 252--301.6) 

This inention relates te luminescent, mate- 
riais. More particu]arly, it relates te arsenic 
tivated zinc su]ride phosphors wh!ch luminesce 
under cathode .ray and ultraviolet excitation. 
With the growing importance of televisión 5 
and other cathode ray tube applications there 
bas been a corresPonding demand for white light 
emitting luminescent materials. There is also a 
need for. such phosphors in the fluorescent light- 
ing field wherein ultraviolet energy isused as the 10 
exciting medium. Heretofore, most of such white 
light emitting phosphors bave been prepared by 
mixing different materials, each haing emission 
bands, which when blended give a resultsut white 
appearing emission. 
It is an object o£ my invention, te proide a 
luminescent material which emits white light 
under cathode raF. and ultraviolet excitation. 
nother object, of my invention is te provide 
such a material in a single substance vith no 20 
need. for blending different materials. 
A further object of my invention is te provide 
a white light emitting phosphor in which the 
shade of white light may be controlled by varFing 
the amoun of activator. 25 
It has been found that such white light emit- 
ring phosphors may be providecl by combining 
with zinc su]ride activating proportions of. ar- 
senic. 
It is known that pure zinc su]ride, when fired 30 
in a pro.tective atmosphere at about 1000 ° C. to- 
gether with a small amount, of fusible sodium 
chloride as a flux, bas a blue omission when ex- 
cited by cathode rays or ultraviolet radiation. 
This blue emission has variously been attributed 35 
te activation by interstitial zinc. " 
Abcording. te tuf invention when small amounts 
of arsenic are added te the zinc su]ride, besie 
the blue celer, emission bands appear also in the 
ozange and gieen portions of the s.uectrum, the 40 
resu]tant overall emission app.earing white te the 
eye. Either the orange or green bands may be 
emphsized by varying the amount of arsenic. 
In. carrying out my invention, arsenic s - adde« 
in the form o a compound such as arsenic tri- 45 
su]ride, arsenic trioxide, zinc arsenate or others  
in such amounts that the added arsenic content 
of the zinc sulflde-arsenic compound mixture 
at le,st 0.01 per cent based on the weiglt of the 
zinc su]ride. The upper limit of arsenic addition 50 
is net strictly defined, amounts up te about rive 
Per cent having been used. However, at such 
high arsenic concentrations the emitted celer is 
green rather than white. For practical purposes 
when a white celer is desired, the arsenic content 5 

ranges from 0.01 per cent.te 2.00 per cenko£the 
starting material with the higher, content hai.ng 
a slight tinge of green under cathodg ray eXcita. tion. Under 3650 . ultraviqie excitation the 
emitted celer ranges from a. warm. Or orangih 
white: at 0.01 per cent arsenic content o. a , light 
greenish white at. 2 per cent. arsenic addition:. 
OEn preparing the present phosphors o lumi.- 
nescent materials the zinc su]ride and arsenic 
compound are thoroughly mixed together, as.by 
grinding,, along with the usual amount of sodium 
chloride.flux as is wel! known in théart. en, 
erallF the amount of flux ranges from abontl.2 
per cent te 6 per cent.of the mixture ¢¢hileso- 
dium chloride is preferred as a flux,, other. alkali 
and alkaline earth halides as well as other fiuxes 
known in the art are, a-lse satisfàctory the. flUX 
itself beini, sUbstantiallF removed fron, the ma- 
terial .after ring and playing no,, role in th_e 
emitted color. 
The phosphors. Of m: invention are 
in a protective hydrogen atmosphere and: are 
fired at temperatures ranging from 800 ° C. te 
1000 ° C. for about onehalf bout. While the re- 
su]tant phosphor is su]table for se, a more 
homogeneous product is obtained by cooling the 
phosphor, regrinding a-nd refiring for about fff- 
teen minutes• at the same temperature. This 
product is then washed free:of flux: and dried. 
Preferably the starting materiäls are red af 
900 ° c. for one-half bout, reground and.' reflred 
at the sarne temperature for flfteen minutes, such 
treatment Producing the whitest emission. In 
general, substantially higher temperatures than 
900 ° C. Produce a luminescent material which 
basan orangish or warm tinge n the white emis- 
sion due fo loss of arsenic. In a series of samples 
co,ntaining one per cent by weight arsenic and 
fired for one-half hour at 800 ° C., 900 ° C., 1000 ° C., 
and 1150 ° Ce, those flred at 800 ° C. and 900 ° 
had a white emission while af the higher tem- 
peratures an orangish white emission resulted. 
The rime of firing af any one temperatnre 
likewise affects the color of the final, product 
• through the loss of arsenic due fo Vaporizatïon. 
In general, substantially longer ring times thon 
one-half hour tend to shift the color of the emit- 
ted light tewards the orange. This is consistent 
with the observation that samples containing 
more than 0.10 per cent by weight added arsenic 
bave less orange in their emission when excited 
by 3650 . ultraviolet. 
The exact amount of arsenic lost during the 
flring process is hot known, no precise technique 
for determining the composition of the final 



2,600,263 

product having been developed. However, a final 
luminescent materîal of consistent composition 
is obtained by startîng with known materîals 
which are treated in a uniform manner. 
The following is indicative of the preferred 
procedure of making my new luminescent mate- 
rials. Ten grain portions of pure zinc sulfide 
were mixed with rive per cent (0.5 gram) bY 
weight of sodium chloride and enough arsenic 
trisulfide to provide respectiely 0.01 per cent, 
0.10 per cent, 0.50 per cent, 1.00 per cent, and 
2.00 per cent .by weight of arsenic based on the 
weight of the zinc sulfide. Preferably the mate- 
rials are mixed by grinding. The samples were 
then flred in hydrogen ai 900 ° C. for one-half 
hour. As pointed out above, while the product of 
thts first flring is suitable for use, a more homo- 
geneous material results if the product is cooled, 
reground, refired ai about 900 ° C. for about 
flfteen minutes, washed with hot distilled water 
to remove the flux and dried. 
The phosphors prepared as above bave, in 
general, three bands in their emission spectra. 
The relative intensity of the bands is dependent 
upon the arsenic concentration in the flnished 
phosphor, the mode of excitation, and the tem- 
perature of the phosphor during excitation. A 
blue hand with a peak ai 4700 A. and due to zinc 
activation of the zinc sulfide appears in all the 
preparations. An orange hand with a peak ai 
6200 A. is aiso evident in all the samples. Rela- 
tive'to the blue hand under 3650 A. excitation, 
:it is most pronounced in the sample containing 
0.1 per cent by weight of added arsenic, and its 
intensity drops off aç higher arsenic concentra- 
tîons. Ai higher arsenic concentrations a green 
hand with a peak ai 5200 A. becomes evident. In 
particular, t is very clearly present in the sample 
containing 2.00 per cent added arsenic. 
The characters ai room temperature of the 
phosphors as prepared above are tabulated 
below: 

Sample 

Weight 
As 
Added 

0.0t 
0. t0 
0.50 
1.00 
2.00 

3650 . Excitation Relative 
Energy 

4700 . 5200 . 6200 .. 

Color Under 
3o .L 
Excitation 

t00 52 68 Warm Wbite. 
100 t 73 200 Light Orange. 
(0 61 80 Warm White. 
6ï 41 Cold Wbite. 
t00 103 21 Light Green. 

Cathode Ray Excitation 
4.7 kv, 5 mtcroamps/Cm .2 
Relative Energy at-- 
Sample 
1 ................... t00  39 | 11 I 
 .........  zoo ! 7 / 2s | 
 ................... 1 oo] so I 

Color Under 
CR 
Excitation 

Light Blue. 
Cold White. 
Do. 
Do. 
Light Grecn. 

4 
intensity of the blue hand so that the color of 
the emitted light tends to shift toward the 
orange. 
For television or other purposes where the 
5 purest or cold whtte color is desirable and cath- 
ode ray excitation is used, materîals having from 
0.10 to 1.00 per cent by weight added arsenic are 
preferred. However, here as well as Ior ultra- 
violet excitation, a variety of phosphors ranging 
10 from orange or orangish-yellow through white 
to green may be produced according to my 
invention by varying the amount of added 
arsenic, the rime of firing, and the temperature 
of flring either singly or în combination. For 
15 example, as pointed out a.bove amounts of 
arsenic up to and above 5 per cent by weight are 
added to produce green color emitting phosphors. 
While I have described my invention through 
the medium of particular examples, it is to be 
20 understood that I desire and intend to protect 
by the appended claires all variations therein 
which do not depart from the spirit and scope o 
my invention. 
What I claire as new and desire to secure by 
25 Letters Patent of the United States is: 
1. The process of preparing a luminescent 
material which comprises mixing with zinc 
sulfide from 0.01 per cent to rive per cent by 
weight of arsenic, from two per cent fo six per 
30 cent by weight of a flux, flring ai 900 ° C. for 
one-half hour, cooling, grinding, reflring ai 900 ° 
C. for fifteen minutes, cooling and washing to 
free of flux. 
2. The process of preparing a luminescent 
35 material whtch comprises mixing with zinc sul- 
ride 0.01% to 5% by weight of arsenic, a flux, 
and flring ai 800 ° C. to 1200 ° C. 
3. The process o£ preparing a luminescent 
material which comprises mixing with zinc 
40 sulfide a flux and 0.01% to 5% by weight of 
arsenic and flring ai 900 ° C. for about one-half 
hour. 
4. The process of preparing a luminescent 
material which comprises mixing with zinc sul- 
ride a flux and 0.01% to 5% by weight of 
45 arsenic, firing ai 900 ° C. for about one-half 
hour, cooling, grinding, and flring ai 900 ° C. for 
about fffteen minutes. 
5. A luminescent material produced by the 
process of claire 1. 
50 6.. A luminescent material produced by the 
process of claim 2. 
7. A luminescent material produced by the 
process of claire 3. 
8. A luminescent material produced by the 
5t process of claire 4. 
JEIOME S. PRENER. 
REFERENCES CITED 
The following references are of record in the 

60 file of this patent: 
UNITED STATES PATENTS 
Number Name 

Date 

Ai excitation temperatures above room rem- 2,074,226 
peratures, the main effect is fo decrease the t 

Kunz ............. Mar. 16, 1937